{"uid":"cap_WMvp9hXyCAlAjoXpo4IrN","slug":"x402node-function-selector-calldata-decoder-895a19e6","name":"x402node Function Selector / Calldata Decoder","description":"Decode a 4-byte function selector or calldata into human-readable Solidity function signatures via openchain - reverses on-chain selectors that LLMs cannot know. function selector, 4byte decode, sig decode, calldata decode, method id, selector lookup","url":"https://api.x402node.dev/chain/sig-decode","method":"GET","headers":{},"bodySchema":{"type":"object","$schema":"https://json-schema.org/draft/2020-12/schema","required":["input"],"properties":{"input":{"type":"object","required":["type","method"],"properties":{"type":{"type":"string","const":"http"},"method":{"enum":["GET"],"type":"string"},"queryParams":{"type":"object","required":["selector"],"properties":{"sig":{"type":"string","description":"Sig (optional)"},"data":{"type":"string","description":"Data (optional)"},"selector":{"type":"string","description":"4-byte selector or full calldata, e.g. 0xa9059cbb (required)"}}}},"additionalProperties":false}}},"responseSchema":null,"example":{"request":{"selector":"0xa9059cbb"},"response":{"note":"Function signatures matching this 4-byte selector (from openchain.xyz). Multiple = hash collisions; verify by context.","_hint":"x402 paid endpoints for AI agents — x402node.dev (utilities) · cn402.com (Chinese culture)","source":"openchain","primary":"transfer(address,uint256)","selector":"0xa9059cbb","matchCount":1,"signatures":["transfer(address,uint256)"]}},"exampleRequest":{"selector":"0xa9059cbb"},"tags":["x402"],"displayCostAmount":"0.004","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"settled","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.004/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.004","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.004","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_PSFFXcPWVSioOw540rrGe","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.004","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Decodes a 4-byte Ethereum function selector or calldata into human-readable Solidity function signatures using the Openchain signature database","exampleAgentPrompt":"Can you decode this Ethereum function selector — 0xa9059cbb — and tell me what Solidity function it maps to?","exampleUseCases":null,"resultDescription":"Returns one or more matching human-readable Solidity function signatures (e.g. 'transfer(address,uint256)') that correspond to the provided 4-byte selector or calldata prefix, drawn from the Openchain on-chain signature registry.","failureModes":["Selector not found in Openchain database — returns empty results or 404 if no known signature matches","Invalid hex format for the selector — returns a 400 bad request error","Selector is only 2 bytes or malformed — parsing error returned","Network or upstream Openchain API unavailable — 502 or timeout error","Rate limit or payment failure — 402 payment required if x402 credit is insufficient"],"whenToPreferThis":"Use this endpoint when you have a raw 4-byte function selector or calldata hex from an Ethereum/EVM transaction and need to identify the human-readable Solidity function signature. Prefer this over manual ABI lookups when the contract ABI is unavailable or unknown, or when working with arbitrary on-chain transactions you did not originate. This is especially useful for transaction analysis, security auditing, or any pipeline where you need to label or understand raw calldata without pre-loaded ABIs.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-09-14T06:49:21.699Z","isFirstParty":false}